MC68HC908AZ60 Datasheet, PDF (117/480 Pages) Motorola, Inc – HCMOS Microcontroller Unit

System Integration Module (SIM)
SIM Counter
SIM Counter
The SIM counter is used by the power-on reset module (POR) and in
stop mode recovery to allow the oscillator time to stabilize before
enabling the internal bus (IBUS) clocks. The SIM counter also serves as
a prescaler for the computer operating properly module (COP). The SIM
counter overflow supplies the clock for the COP module. The SIM
counter is 12 bits long and is clocked by the falling edge of CGMXCLK.
SIM Counter
During Power-On
Reset
The power-on reset module (POR) detects power applied to the MCU.
At power-on, the POR circuit asserts the signal PORRST. Once the SIM
is initialized, it enables the clock generation module (CGM) to drive the
bus clock state machine.
SIM Counter
During Stop Mode
Recovery
The SIM counter also is used for stop mode recovery. The STOP
instruction clears the SIM counter. After an interrupt, or reset, the SIM
senses the state of the short stop recovery bit, SSREC, in the CONFIG-1
register. If the SSREC bit is a logic one, then the stop recovery is
reduced from the normal delay of 4096 CGMXCLK cycles down to 32
CGMXCLK cycles. This is ideal for applications using canned oscillators
that do not require long start-up times from stop mode. External crystal
applications should use the full stop recovery time, that is, with SSREC
cleared.
SIM Counter and
Reset States
External reset has no effect on the SIM counter. See Stop Mode on page
122 for details. The SIM counter is free-running after all reset states. See
Active Resets from Internal Sources on page 111 for counter control and
internal reset recovery sequences.
11-sim
MOTOROLA
System Integration Module (SIM)
MC68HC908AZ60 — Rev 2.0
115